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Length of this time unit: Length of time between the midnight (UTC) closest to the December Solstice and the midnight (UTC) closest to the next December Solstice–either 365 or 366 days.


The length of the year should be the same as it is now with almost all calendars, because the length of the year on Earth has been remarkably constant, going almost all the way back to our planet’s beginning.

However, if you were to ask the average person how long a year is, they’d say 365 days except for Leap Year when it’s 366 days.  Neither figure is accurate. The actual length of the year is in between–what changes is the time of day upon which it falls.  The mean tropical year is 365.2422 days.

The Gregorian calendar, despite its almost universal use, is not the most accurate calendar in the world. That honor actually belongs to the Solar Hijri calendar used in Iran and Afghanistan. Both calendars have leap years with leap days, but the Gregorian leap years are mathematically fixed while the Solar Hijri leap years are astronomically fixed.  The Solar Hijri calendar simply measures the year as being between the midnight closest to the Northward (Spring) Equinox and the midnight closest to the next Northward Equinox. Most of the time it means that leap years are four years apart, but once in a while they are five years apart. You can see from the charts below that the Gregorian calendar’s formula allows the beginning of the tropical year to vary by as much as 2-3 days, while the Solar Hijri calendar limits that variability to just ten hours or so.

By BasZoetekouw; spelling corrections and revision of subtitle by User:Gerry Ashton on 14 September 2008. – Own work; The data was generated by Astrolabe (, which uses the algorithms described in Jean Meeus’s “Astronomical Algorithms” (ISBN 978-0943396613). The data have an error of less than 2.6 minutes., CC BY 3.0,











Jalaali Leap Year differentials
By Joel Bradshaw – Own work, CC BY-SA 4.0,











As such, the Earth Epic Calendar is also astronomically set. It sets the first day of the year at the Winter Solstice (rather than the Solar Hijri’s Spring Equinox) for several reasons. First, the adjustment from the Gregorian Calendar—the mostly widely used calendar in the world—is less difficult because the first day of the year in the Earth Epic calendar is just 10 or 11 days before the first day of the year in the Gregorian calendar, making adjustments easier. The Winter Solstice also coincides with holidays for many religions and cultures. This time is also often the midpoint between the autumn harvest and the spring planting season for much of the world, given that 90% of human beings live in the Northern Hemisphere.  So for many people around the world, this period around the Winter Solstice is often a time for pause and reflection.

However–as is true of the Solar Hijri Calendar–this astronomical-based means that the incidences of the leap year are slightly more irregular than the Gregorian Calendar. Most of the time four years pass between leap years, but occasionally the interval is five years. In the Earth Epic calendar, the year 11721 (which began on 12/21/2020), the last one was 11717, (which began on 12/21/2016) and the next one will be on 11725 (starting 12/21/2024). The last five year interval between leap years was between 11708 and 11713 and the next one will be between 11741 and 11746. (As said before, the Year is based on the first year of the current Epoch being 9701 BCE, which is 11,700 years BCE before 2000 CE.)

An advantage of the Gregorian mathematical methods of determining the leap years vs the Earth Epic and Solar Hijri astronomical methods is that no astronomical observance is necessary in order to plot the new year.  However, our ability to predict the date and time of the next South Solstice is well-established.  A chart on this website shows the precise date and time of the South Solstice starting on the solstice after the Gregorian calendar was established in 11283 (1583 CE) and the year 12000 in the Earth Epic calendar (from the South Solstice of 2299 CE to the South Solstice of 2300).

Expressing the year

With the year being 1/25,000th of an Epoch, wouldn’t there be any value in making a Century or Millennium an official time scale?  After all, the Eon, Genesis, and Epoch are each separated by factors of one hundred.  To then suddenly leap to a factor of 25,000 seems inconsistent.

Indeed, the earliest versions of this calendar did include the century.  The rationale at the time is in people’s minds, the centuries are very different from each other.  Also, there is the added convenience of being able to use the same two-digit number to express the year in both the Gregorian and Earth Epic Calendars.

But in subsequent versions of this calendar, the century was replaced with the millennium as the standard.  The reason being is that it is easier to distinguish the millennia from each other and it’s easier to imagine 25 millennia in an Epoch than 250 centuries.

Truly, we don’t know what people will find most convenient in the future.

It was interesting to see how when the year 2000 CE arrived, people began to write the date using four years more often, and we began to see more instances where people would write 1/1/2000 rather than 1/1/00.  It made sense–the new millennium was a novelty and people wanted to feel a part of it.  It’s reasonable to expect that people will do the same with the five-digit year in the Earth Epic Calendar.

I catch myself writing “Year 21” when talking about the year just to keep that universality.

But I also can’t rule out people deciding in the future to expressing the millennium as something separate, and expressing the year by its last three digits.

It’s noteworthy that for a four digit year, people suspend the normal habit of putting a comma between the thousands digit and the hundreds digit.  People will more likely write 2021 than 2,021.  Will people continue to waive the comma for a five digit year?  Maybe, maybe not.

Truly, we don’t know what people will find most convenient in the future.  So it makes more sense to let people decide, just as how people around the world decide whether to put the day, the month ojr the year first when expressing the date.

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